Freshwater snails of the Bulinus forskalii group are one of four Bulinus species complexes responsible for the transmission of schistosomes in Africa and adjacent regions. The species status of these conchologically variable and widely distributed planorbids remains unclear, and parasite compatibility varies considerably amongst the eleven taxa defined, making unambiguous identification and differentiation important prerequisites for determining their distributions and evolutionary relationships. Random Amplified Polymorphic DNA (RAPD) analyses were used to investigate relationships between taxa, with particular emphasis on Central and West African representatives. RAPD-derived phylogenies were compared with those from other independent molecular markers, including partial sequences of mitochondrial cytochrome oxidase subunit I (COI) gene, and the nuclear ribosomal RNA internal transcribed spacer 1 region (ITS1). The phylogenetic reconstructions from the three approaches were essentially congruent, in that all methods of analysis gave unstable tree topologies or largely unresolved branches. There were large sequence divergence estimates between species, with few characters useful for determining relationships between species and limited within species differentiation. Nuclear and mtDNA sequence data from Central and East African representatives of the pan-African B. forskalii showed little evidence of geographical structuring. Despite the unresolved structure within the phylogenies, specimens from the same species clustered together indicating that all methods were capable of differentiating taxa but could not establish the inter-specific relationships with confidence. The limited genetic variation displayed by B. forskalii, and the evolution and speciose nature of the group, are discussed in the context of the increasingly arid climate of the late Miocene and early Pliocene of Africa.

The effects of metacestodes of Hymenolepis diminuta on haemolymph proteins of Tenebrio molitor are restricted to female hosts. In beetles aged 15 days post-emergence, and harbouring 12-day-old metacestodes, haemolymph concentration is 46·7% higher than in non-infected animals and similar effects are found in longer standing infections. Electrophoresis of haemolymph revealed the presence of 13 bands. Densitometric analysis showed that only band 2/3 was significantly elevated in infected hosts although band 7/8 also showed an increase. These bands were also present in egg homogenates and are thought to be vitellogenins. It is therefore proposed that the excess protein found in infected beetles is a female-specific protein resulting from an interaction between the parasite and the host endocrine system.

A Leishmania infantum cDNA library was screened with sera from dogs with viscero-cutaneous leishmaniasis. Sequence analysis of a positive clone isolated from the library revealed that it coded for the carboxyl-terminal region of a member of the 70-kDa heat-shock protein family. The full-length sequence of the L. infantum hsp70 gene was determined after isolation of genomic clones. This protein shows a high degree of sequence conservation with the homologous protein from other organisms. To test its antigenicity a recombinant Hsp70 protein fused to the maltose-binding protein was produced in Escherichia coli using the expression vector pMAL-cRI. By FAST-ELISA assays it was observed that while the complete recombinant protein was recognized by 100% of the sera, the 20 carboxyl-terminal amino acids of the protein were only recognized by 30% of those sera. Thus, although a B-cell epitope must be present within the carboxyl terminal end of the protein other antigenic determinant(s) must reside out of this region. The analysis of the cross-reactivity with mouse Hsp70 by Western blotting strongly suggests that the anti-Hsp70 antibodies generated by infection with L. infantum are directed at specific determinants of the L. infantum Hsp70. Thus, our results indicate that anti-Hsp70 autoantibodies are not induced during Leishmania infection.

Caraphractus cinctus Walker is a parasitoid of the eggs of Dytiscidae. The entire development of this Mymarid takes place in eggs immersed in water and attached to, or embedded in, plant tissue. The winter is passed in diapause as a full-grown resting larva (prepupa) in the host egg.

Diapause of Caraphractus has been studied in the eggs of Agabus bipustulatus. The eggs of this Agabus do not undergo diapause and since the shell is transparent, the larvae of Caraphractus (usually two to three in each egg) are clearly visible during their later stages, so the time of pupation is easily determined.

Experiments were made of chilling the maternal generation of Caraphractus at various stages of development, but this did not lead to diapause in the larvae of the chilled generation, or to any increase in the diapause in the offspring.

When the Mymarid was bred in a north room exposed to natural daylight and darkness, some diapausing larvae occurred in mid-September and by October all were in diapause.

When larvae were reared in long photoperiods (16½–24 hr. light) development was direct, but with short photoperiods (2–15 hr. light), diapause occurred. The critical period lies between 14 and 16 hr. of light.

The stage sensitive to photoperiod is the full-grown larva, and when larvae are reared to this stage under short photoperiod and then transferred to continuous light, direct development is determined within 3 days. Conversely, larvae reared under continuous light and removed to short photoperiod before reaching the sensitive stage, go into diapause.

The larvae are sensitive to light of very low intensity, developing direct with a ‘night’ of 0·03–0·05 f.c. Larvae becoming full grown in the end of August and beginning of September do not diapause and must respond to 2–3 hr. of twilight.

Diapause induced, under artificial photoperiods at any time of the year, usually lasts about as long as the normal winter diapause. If however the prepupae are subjected to temperatures below freezing for about a fortnight (provided they have already been about 15 weeks in diapause) pupation occurs as soon as the temperature is suitable. In cold weather the pupal stage may be greatly prolonged.

I am much indebted to Professor H. G. Callan for his kind permission to use the constant temperature rooms at the Natural History Department of St Andrews University. I have received most valuable help from Dr C. Muir in conducting the various photoperiod experiments, especially in regard to light measurements, and I am most grateful to him for discussing with me many of the problems that arose in the course of this research and for commenting on the typescript of this paper. To Dr H. E. Hinton I am indebted for useful advice, and to Dr Seliga of St Andrews University for his translation of Russian papers. Professor and Mrs Stibbs have been most kind in providing me with information regarding the duration of astronomical darkness in the latitude of St Andrews. I am especially grateful to Dr George Salt for his kindness in reading over my typescript and for his helpful criticisms.

Eggs of Oesophagostomum dentatum in faeces deposited on grass plots from May to October developed into infective larvae. Warm wet weather facilitated development but weather conditions which caused the faeces to dry out rapidly resulted in a heavy mortality of eggs and pre-infective larvae. During the winter no development took place and the eggs died. In the early spring and late autumn a few eggs survived and developed into 1st-stage larvae but they died without developing further. In the laboratory no development took place at 4 °C but at temperatures ranging from 10 to 25 °C development into infective larvae was completed, the rate increasing as the temperature rose. Out-of-doors infective larvae survived in faeces and on herbage for 1 year under a wide range of climatic conditions including the exceptionally cold winter of 1978–79. In the laboratory, infective larvae suspended in water survived even longer at temperatures ranging from 4 to 27 °C. They were rapidly killed by continuous freezing and by desiccation when the relative humidity was less than 90%. The relationship between climatic conditions and the development and survival of the free-living stages is discussed.

Clinical isolates from 3 microsporidia species, Encephalitozoon intestinalis and Encephalitozoon hellem, and the insect parasite Anncaliia (Brachiola, Nosema) algerae, were used in spore germination and enterocyte-like (C2Bbe1) cell infection assays to determine the effect of a panel of antimicrobial peptides. Spores were incubated with lactoferrin (Lf), lysozyme (Lz), and human beta defensin 2 (HBD2), human alpha defensin 5 (HD5), and human alpha defensin 1 (HNP1), alone and in combination with Lz, prior to germination. Of the Encephalitozoon species only E. hellem spore germination was inhibited by HNP1, while A. algerae spore germination was inhibited by Lf, HBD2, HD5 and HNP1, although HBD2 and HD5 inhibition required the presence of Lz. The effects of HBD2 and HD5 on microsporidia enterocyte infection paralleled their effects on spore germination. Lysozyme alone only inhibited infection with A. algerae, while Lf inhibited infection by E. intestinalis and A. algerae. HNP1 significantly reduced enterocyte infection by all 3 parasite species and a combination of Lf, Lz and HNP1 caused a further reduced infection with A. algerae. These data suggest that intestinal antimicrobial peptides contribute to the defence of the intestine against infection by luminal microsporidia spores and may partially determine which parasite species infects the intestine.

Abomasal and duodenal motility was investigated by electromyography in 4 lambs fitted with permanent abomasal and duodenal cannulae and infected twice with 25000 Haemonchus contortus larvae at an interval of 39 days. In addition, abomasal and duodenal pH, flow rate of digesta of the duodenum, and faecal water content were determined. The 80–90 min cycles of antral contractions were shortened for at least 3 weeks after infection. This was accompanied by a 26% increase in the number of duodenal migrating myoelectric complexes/day during the intra-parietal development of the larvae (10–12 days). Concomitantly, the duodenal flow of digesta increased from 215 ± 22 ml/h to 318 ± 15 ml/h 4 days after infection and was associated with a higher water content of the faeces. The frequency of the migrating myoelectric complexes, but not the duration of antral motor cycles (or the duodenal flow rate), was correlated with both gastric (P < 0·01) and duodenal (P < 0·05) pH after the first and second infections. The duodenal flow rate was correlated with the Cl− concentration of the abomasal contents (P < 0·01) and with the duodenal pH (P < 0·05). It is concluded that, (i) the duodenal motor disturbances associated with experimental H. contortus infection are related to the alterations in abomasal gastric acid secretion which occurs during the histotrophic phase of larval development and (ii) the increased duodenal flow is a consequence of ionic permeability changes of the gastro-intestinal mucosae.

Chagas infection is a major endemic disease affecting Latin American countries. The persistence of Trypanosoma cruzi generates a chronic inflammatory reactivity that induces an immune response directed to the host's tissues. The effectiveness of the treatment in the chronic phase is still unsatisfactory due, amongst other reasons, to the collateral effects of the drugs used. We investigated the effect of clomipramine, a tricyclic antidepressant that, when used as a treatment of T. cruzi-chronically infected mice, inhibits trypanothione reductase, an exclusive and vital enzyme of T. cruzi. Clomipramine improved survival (P<0·05) by diminishing the parasite intensity as demonstrated by PCR studies in the heart and skeletal muscle, and significantly prevented the evolution to fibrosis of the inflammatory infiltrates. Clomipramine could be a good candidate for the treatment of chronic Chagas disease.

In recent years, the isolation of parasitic DNA from faecal samples and PCR techniques, have been improved and simplified. Moreover, the introduction of real-time PCR has made it possible to multiplex different targets into one reaction. These new technical possibilities make it feasible to introduce PCR with its unsurpassed sensitivity and specificity in a routine laboratory setting for the diagnosis of intestinal parasites. Detection rates of the parasitic infections included in the PCR are increased significantly compared with microscopy. Molecular diagnostics, especially in children, reveal a possible cause of the gastrointestinal complaints in many more cases compared with conventional methods. Usually in GP patients no other pathogenic parasites are detected using microscopy and in the returning travellers additional parasites are found with microscopy in a minority of cases only. Multiplex real-time PCR offers a highly sensitive and specific diagnostic alternative for labour intensive microscopy in clinical laboratory practice. Additional diagnostic methods for the detection of parasitic infections that are not included as PCR target can be limited to a selected group of patients.

The composition and diversity of metazoan parasite communities in naturally depauperate ecosystems are rarely studied. This study describes the composition of helminth endoparasite communities infecting fish that are part of naturally acidic stream ecosystems in the coastal-plains region of the State of New Jersey (USA) known as the Pinelands, and compares the diversity of parasites between six streams that differ in anthropogenic disturbance. A total of 514 fish were examined representing 6 species native but restricted to the Pinelands region, 5 species native and widespread throughout the region and State, and 6 species introduced to the Pinelands and State. Fish (prevalence: 78%) were infected with 18 helminth endoparasite species. In most streams, prevalence of infection, mean abundance, and total number of individuals for the 5 most common parasites were higher in pirate perch, a native fish species. The diversity of helminth endoparasite communities measured as species richness and Shannon index was higher in degraded streams, and especially in native or introduced fish at these sites. Parasite diversity was positively correlated with anthropogenic disturbance, which was measured by water pH, water conductance, and the proportion of agricultural and developed land surrounding streams. Helminth community composition included parasites intimately tied to trophic interactions in food webs, and disturbance to these ecosystems results in changes to these communities. Understanding structure and function of animal communities from these naturally depauperate ecosystems is important before continued anthropogenic changes result in the extirpation or extinction of their unique fauna.

A hypothesis has been erected stating that in the British Isles the acanthocephalan, Pomphorhynchus laevis can be separated into 3 strains, an English, Irish and marine strain. Ecological and morphological evidence exists in support of this hypothesis. An investigation at the molecular level was conducted in order to test the validity of the existing evidence. A mitochondrial gene, subunit I of cytochrome c oxidase was partially sequenced from 3 Irish populations of P. laevis, 1 Scottish population and 3 English populations. P. laevis sequences from brown trout from Ireland, England and Scotland were very similar, showing a mean sequence divergence of 0·7%. Sequences from two populations of P. laevis from English chub and bullhead were also similar to each other (0·35% divergence). These two groups of sequences, the brown trout group and the chub/bullhead group were 2·2% different. These data confirm the existence of at least 2 strains in Ireland and Britain, although there is evidence to suggest that these strains are defined by their host species rather than by their geographical distributions.

Proteinase activities were examined in extracts and excretory–secretory (ES) products of the infective and adult stages of the cattle lungworm, Dictyocaulus viviparus. Multiple enzyme activities were identified from each source, as defined by pH optima, substrate specificities, inhibitor effects and substrate gel electrophoresis. Serine-, cysteine- and metalloproteinases were identified, secreted materials being more active against protein substrates per unit protein than were extracts, and the particular proteinases produced varied with the developmental stage of the parasite. The antigenicity of these parasite proteinases was demonstrated by the inhibition of enzymic activity with Protein G-purified serum IgG antibody from both infected and vaccinated hosts and in the retardation of enzyme migration on electrophoresis of enzyme–antibody complexes. For the adult products, this confirmed that the enzymes concerned were of parasite origin, and not host-derived. These results argue for investigation of D. viviparus proteinases as targets for the antibody response in the limitation of parasite-mediated tissue damage and as the active principle behind the anti-D. viviparus vaccine.

Rats can be passively protected against N. brasiliensis either with antiserum or with cells. Only some pools of antiserum (15 of 48 pools) and a few batches of cells (three of 11 batches) were protective.

Protective activity was found in serum taken after one infection as frequently as after several infections and gave the same degree of protection. This suggests that second and subsequent infections do not stimulate an anamnestic increase in protective antibodies in the circulation.

Serum and cells taken from the same rats were unrelated in their protective capacity; sometimes serum protected when the cells were ineffective and the reverse also occurred.

Cells transferred from the spleen, peritoneal cavity or mesenteric lymph nodes were capable of initiating reagin formation, irrespective of their ability to protect against N. brasiliensis.

When protection was achieved with transferred cells, the parasite life-cycle was shortened by only 1–2 days.

We have found no evidence that a delayed mechanism of the homograft type is concerned in immunity to N. brasiliensis in the rat.

We thank Miss W. D. Griffiths and Mr A. J. Edwards for their willing assistance. The statistical analysis was kindly done for us by Miss M. V. Mussett of the Statistics Department at our Institute.

Schistosoma haematobium is refractory to praziquantel (PZQ) during the prepatent period of infection. A hypothesis based on this observation is that in areas where S. haematobium transmission is seasonal, the outcome of chemotherapy depends on the timing of the treatment relative to the annual transmission pattern. To examine this hypothesis, a study was carried out in southern Mozambique. Following demonstration of seasonal transmission, PZQ was administered separately to two cohorts of S. haematobium-infected schoolchildren in (1) the high and (2) the low transmission seasons and followed up after two months when levels of infection and intensities were measured. The prevalence of infection decreased from 54·2% and 51·7% in cohorts 1 and 2 to 30·3% and 1·8%, respectively. The geometric mean intensity of infection decreased from 23·3 eggs/10 ml of urine at baseline to 15·6 eggs/10 ml of urine in cohort 1 (treated during high transmission season), and from 23·5 eggs/10 ml urine to 7·3 eggs/10 ml of urine in cohort 2 (treated during low transmission season). The observed cure rates in cohorts 1 and 2 were 69·7% and 98·2%, respectively. Differences in infection between the cohorts in terms of cure rate and level of infection two months post-treatment were statistically significant and indicate that in areas with a seasonal transmission pattern, the effect of PZQ can be enhanced if treatment takes place during the low transmission season. We conclude that appropriately timed PZQ administration will increase the impact of schistosomiasis control programmes.

Target-based approaches for human African trypanosomiasis (HAT) and related parasites can be a valuable route for drug discovery for these diseases. However, care needs to be taken in selection of both the actual drug target and the chemical matter that is developed. In this article, potential criteria to aid target selection are described. Then the physiochemical properties of typical oral drugs are discussed and compared to those of known anti-parasitics.

The immunogenicity of the secretory exo-antigen (EXA) originating in the stichosome of Trichuris muris has been investigated. High levels of immunity to challenge were produced using EXA (100 μg) by subcutaneous administration. Vaccination with a range of doses of EXA in Freunds' Incomplete Adjuvant (FIA) showed a dose response; 1 μg of EXA reduced the worm burden by 50% and doses of 10 μg or more reduced the worm burden by 80–90% at Day 9 post-infection. Worms recovered from vaccinated mice were significantly smaller than those from controls. A precipitin line identifiable with EXA was shown to immunize mice against T. muris challenge by vaccination. The protective antigen contained in EXA has been partially isolated using gel filtration, ion exchange filtration and isoelectric focusing and has been shown to be a protein of 30000 molecular weight having a pi of 6·8–7·3.

Antigenic variation in malaria was discovered in Plasmodium knowlesi studies involving longitudinal infections of rhesus macaques (M. mulatta). The variant proteins, known as the P. knowlesi Schizont Infected Cell Agglutination (SICA) antigens and the P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) antigens, expressed by the SICAvar and var multigene families, respectively, have been studied for over 30 years. Expression of the SICA antigens in P. knowlesi requires a splenic component, and specific antibodies are necessary for variant antigen switch events in vivo. Outstanding questions revolve around the role of the spleen and the mechanisms by which the expression of these variant antigen families are regulated. Importantly, the longitudinal dynamics and molecular mechanisms that govern variant antigen expression can be studied with P. knowlesi infection of its mammalian and vector hosts. Synchronous infections can be initiated with established clones and studied at multi-omic levels, with the benefit of computational tools from systems biology that permit the integration of datasets and the design of explanatory, predictive mathematical models. Here we provide an historical account of this topic, while highlighting the potential for maximizing the use of P. knowlesi – macaque model systems and summarizing exciting new progress in this area of research.

The levels of superoxide dismutase (SOD) were determined in detergent-soluble, somatic and excretion–secretion (E–S) preparations from adult Fasciola hepatica using the xanthine oxidase system and visualized in substrate gels. Compared to detergent-soluble and somatic extracts, E–S products showed the highest SOD activity (88 ·5 U/mg), indicating active release to the medium in which parasites were maintained. SOD specific activity was also detected at high levels in E–S products from 3-week-old and 5-week-old immature migrating flukes (25 and 143 U/mg, respectively). In all preparations except for the somatic extract, the activity was characterized as cyanide-sensitive CuZn SOD. Differences in SOD isoenzyme profiles between the extracts were observed in native polyacrylamide gel electrophoresis: the somatic and detergent-soluble extracts exhibited 1 band of activity while the E–S products from immature and adults flukes contained 2 and 3 migrating bands, respectively. SOD was purified from the detergent-soluble extract and E–S products of adult worms by a combination of ultrafiltration, gel filtration on Sephacryl S-200 HR and ion-exchange chromatography on QAE Sephadex A-50. The SOD from detergent-soluble extract showed, by SDS–PAGE analysis, 1 band of 16 kDa apparent molecular weight. The SOD from E–S products showed 2 bands of 16 and 60 kDa apparent molecular weight. N-terminal sequence analysis of the 16 kDa band from the detergent-soluble preparation showed some similarity with Schistosoma mansoni cytoplasmic SOD. These enzymes may have a potential role in the evasion of the oxidative burst killing mechanism by immune cells.

1. Six species of Amitermes, one from Panama and five from California, have been examined for protozoa. Certain protozoa have been found in many or all individuals examined of all species, but they are much less abundant than are flagellates in termites of the three xylophagous families below the Termitidae.

2. Trichomonas lighti n.sp. has been found in all species, but not in all individuals.

3. Chilomastix minuta n.sp. occurs in Amitermes beaumonti.

4. Embadomonas termitis n.sp. is described from Amitermes beaumonti.

5. Endamoeba beaumonti n.sp. has been observed in five host species. In its size and nuclear structure it resembles Endamoeba disparata of Mirotermes hispaniolae.

6. Nyctotherus silvestrianus n.sp. has been found in three of the Californian species. It resembles N. termitis and N. ovalis, but is larger than the former and smaller than the latter. A long filament is attached to the end of the cytopharynx. A thickened, V-shaped structure lies against the cyto-pharynx. Several deeply staining fibrils arise from this V.

7. A coccidian has been found in one individual of Amitermes minimus. This forms sixteen banana-formed merozoites and three sporoblasts as in Chagasella.

8. Micro-organisms other than protozoa are very abundant in the intestines of all six species of Amitermes, and they are similar in all.

During the course of a field study of coccidiosis in turkeys, Eimeria oocysts were found which had much smaller dimensions than any previously recorded isolate from the turkey. These oocysts were purified by single oocyst infection of a turkey. The first oocysts (mean dimensions 16.15 ×14.75 μm) were recovered 103 h later. Inoculation of between 0·5 and 2.5 ×105 oocysts of this isolate caused severe effects on body weight gain. Cross-immunity studies showed the parasite to be a strain of E. meleagrimitis. Electrophoretic analyses of two enzymes showed that the strain could be differentiated from another strain of E. meleagrimitis. (Weybridge strain B).

The results show that strain variation occurs within the species E. meleagrimitis and extreme caution should be used in identifying species of Eimeria from the turkey by their oocyst characters.